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-   -   Deep sand bed... black. Help (http://www.reefcentral.com/forums/showthread.php?t=1872904)

NotAPiscivore 07/05/2010 04:29 PM

Deep sand bed... black. Help
 
I am currently running I think what you would call a deep sandbed 3-4" of southdown a 28g nano. If you go below the surface about a 1/4" the sand has turned black and looks like decayed organic matter. If I use a turkey baster and suck up the sand, the removed sand and water look like I rinsed carbon in it (dark grey). So my question should it look like this (black below the surface)? I know a deep sand bed should not be disturbed but this concerned me.

The reason I was investigating is that entire sand bed is having a cyano problem. I was gone for 3 weeks and I lost a brain coral when the tank was being baby sat. So I wasn't sure if the cyano was just due to the coral death and I can expect it to clean up or if it is to decaying organic matter in the sand.

Hoping not to have to pitch the sand but I'll do it if I need to.

NotAPiscivore 07/05/2010 04:30 PM

Oh, and corals are fine and so are the water parameters.

mangobusa83 07/05/2010 06:00 PM

My 72gal has roughly 4 to5 inch sand bed and has some darker colors under the surface bout 2 to 3 inches down from the surface... I think its common but Id wait to see what others say

medic29 07/05/2010 06:41 PM

That's normal. when I took my 120 down to move, all of the sand was dark below the surface. If you pull it out it will stink to high heavens as well.

Sloeber 07/06/2010 10:03 AM

The black is from what is called the anoxic zone, or without oxygen. Essentially, this is present in all reef aquariums, even those without sandbeds. The inner core of LR also has zones of anoxia. These areas of no O2 is where our anaerobic bacteria live and continue the path of breaking down the dissolved organic compounds. By the time the DOC's are finished in the anoxic zone, they are released in the form of a gas (nitrogen IIRC) (the gas bubbles you see along the glass pane in your DSB or suddenly rise from your DSB).

Literally speaking, that black zone is what you are trying to recreate with your DSB. So that's good that you have it. However, I'm concerned with how near the surface you are finding it. This tells me two things - 1) you lack enough DSB "critters" (everything from worms and pods to cucumbers and conchs) to sufficiently turn over your sand and 2) you didn't vary grain size of the sand (guessing you used Southdown exclusively) and the sand is becoming compacted near the surface.

Is this bad? No, not if you don't touch it and let it do it's thing. However, if you go in and stir it all up, that's not good. Everytime you see black, you are essentially burning the anerobic bacteria with O2 (killing it). So don't do that (LOL).

HTH


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